Zoo Atlanta has received a $5 million gift — the largest private donation in its history — from the Joseph B. Whitehead Foundation, the Atlanta Business Chronicle reports.

Awarded as part of the zoo's $25.7 million capital campaign, the gift will support the construction of a new amphibian and reptile complex. Designed in the late 1950s, the existing reptile complex opened in 1962. "It was one of the few buildings that didn't get redone when we rejuvenated the zoo," Zoo Atlanta CEO Raymond King told the Chronicle. "A lot of the collections are not even on display. It's one of the most depressing buildings we have."

Indeed, Zoo Atlanta made headlines after a rattlesnake escaped from an unsecured cage in the reptile house last year. Although the rattlesnake was found, the reptile complex has been deemed an accreditation liability. According to King, the zoo was told it needed to "deal with the reptile building because it is beyond its useful life."

When it opens in 2013 or 2014, the new complex will cover about 1.5 acres of land and include 18,000 square feet of interior habitat exhibits — doubling the existing 9,000-square-foot reptile house — viewing areas, comfort facilities, boardwalks, and a theater.

"The zoo's plans are very exciting," said Russ Hardin, president of the Whitehead Foundation, which is part of the Robert W. Woodruff family of foundations. "We have gone from having one of the worst zoos in the country to one of the best. The reptile house is unfinished business in that transformation."